Ronald T. Stanko

Development of hepatic cholestasis and fibrosis in patients with massive loss of intestine supported by prolonged parenteral nutrition.

We studied the effect of 1 yr of parenteral nutrition on liver function tests and, when indicated, liver histology and ultrastructure of 18 patients with no (n = 6), modest (n = 6), and massive (n = 6) loss of intestine. The resection was for Crohns disease and infarction, respectively. The liver function tests remained normal in all patients with no loss and modest loss of intestine. Four patients with massive loss of intestine, 4-10 mo after initiation of parenteral nutrition, began to develop progressive, marked increases in serum alkaline phosphatase (2-10 times normal), glutamic oxaloacetic transaminase (7-20 times normal), and glutamic pyruvic transaminase (5-14 times normal) activity levels, and bilirubin concentration (5-22 times normal). Light microscopic examination of liver showed cholestasis, bile ductular proliferation, periportal inflammation, fibrosis, and mild steatosis. Electron microscopic examination of liver showed cholestasis with nonspecific organelle changes. None of the patients had any evidence of extrahepatic obstruction. Our data suggest that massive loss of intestine is a contributing factor to hepatic cholestasis and fibrosis in patients maintained on prolonged parenteral nutrition.

Pyruvate prevents ischemia-reperfusion mucosal injury of rat small intestine

BACKGROUND Since reactive oxygen intermediates (ROI, or free radicals) have been implicated in the pathogenesis of ischemia-reperfusion injury of the small bowel, we evaluated the pretreatment effect of pyruvate, a 3-carbon compound recently shown to inhibit superoxide production, on reperfusion mucosal injury in the rat. METHODS The small bowel of the ACI rat (n = 6) was divided into 2 5-cm segments, and 10 mL of a liquid diet containing pyruvate (0.32 g) or placebo (0.26 g) was instilled into the lumen of one of the segments for 10 minutes. The bowel was then made completely ischemic for 45 minutes by clamping the superior mesenteric artery, which was followed by 60 minutes of reperfusion. RESULTS The production of ROI in bowel biopsy samples, estimated by luminol-enhanced chemiluminescence, was at least 80% decreased in the segment containing pyruvate compared with placebo immediately after ischemia (time 0), and compared with 30 and 60 minutes of reperfusion (P < 0.05 for each time point). After 60 minutes of reperfusion, the bowel segment containing the placebo diet showed villus sloughing with destruction of lamina propria and crypts, and mucosal neutrophil infiltration had increased by 80%. Electron microscope evaluation revealed a reduction in number and size of microvilli, dilatation of intercellular spaces, and intracellular vacuoles. The bowel segment containing pyruvate showed the villi and crypts to be intact, without enhanced neutrophil infiltration. CONCLUSION Pyruvate pretreatment of the rat small bowel inhibits postischemic reperfusion mucosal histologic injury, neutrophil infiltration, and ROI production.

Fasting-enhanced immune effector mechanisms in obese subjects

Acute nutritional deprivation occurs frequently in clinical practice, yet little data exist on its effect on immune host defenses. To investigate this question, various immune parameters were studied in 15 obese subjects before and after a 14-day fast. Blood monocyte bactericidal activity and natural killer cell cytolytic activity were enhanced by fasting: monocyte killing increased in 12 of 14 subjects (p less than 0.05) and natural killer cell activity increased an average of 24 percent in 13 subjects tested (p less than 0.02). Starvation also enhanced parameters of humoral immunity as evidenced by increases in serum concentrations of IgG, IgA, and IgM (p less than 0.01). By contrast, lymphocyte blastogenic responses to the mitogen phytohemagglutinin were modestly decreased. Peripheral blood leukocyte counts, including neutrophils, T cells, and B cells, did not decrease significantly. These results indicate that fasting has differential influences on immune function rather than a uniformly deleterious effect. Of potential import, this nutritional alteration appears to actually enhance certain effector functions of the host defense system.

Blood glucose extraction as a mediator of perceived exertion during prolonged exercise

SummaryThe effect of blood glucose extraction on the perception of exertion was examined during prolonged arm exercise. Eight male subjects consumed in counterbalanced order a standard daily diet containing either (1) 75 g dihydroxyacetone and 25 g sodium pyruvate (DHAP) or (2) an isocaloric amount of placebo, to manipulate blood glucose extraction. Following each 7-day diet, subjects exercised to exhaustion at 60% of peak arm oxygen consumption. Ratings of perceived exertion (Borg, CR-10 scale) were obtained for the arms (RPE-A), legs (RPE-L), chest (RPE-C) and overall body (RPE-O) every 10 min of exercise. After 60 min of continuous exercise, blood samples were drawn from the radial artery and axillary vein. Ratings of perceived exertion did not differ between trials during the first 50 min of exercise. At the 60-min time point, perceived exertion was lower (P < 0.01) in the DHAP than placebo trials for the arms (RPE-A: 4.25 vs 5.50) and overall body (RPE-O: 3.25 vs 4.00). These differences persisted throughout exercise. RPE-L and RPE-C did not differ between trials. Whole-arm arterial-venous glucose difference was higher (P < 0.05) in the DHAP (1.00 mmol · 1−1) than placebo (0.36 mmol·1−1) trials, as was fractional extraction of glucose (22.5 vs 9.0%). Respiratory exchange ratio was the same between trials. Triceps muscle glycogen was (1) higher in the DHAP than placebo trial at pre-exercise (P < 0.05), (2) decreased during exercise and (3) did not differ between trials at exercise termination. Free fatty acids, glycerol, β-hydroxybutyrate, lactic acid, pH, norepinephrine and epinephrine did not differ between trials. These findings suggest that blood glucose extraction mediates the perceived intensity of exertion arising from active limbs during prolonged arm exercise.

Modulation of leucine oxidation and turnover by graded amounts of carbohydrate intake in obese subjects

Our previous in vitro studies with rat tissues have suggested that ketone bodies may regulate the oxidation of branched-chain amino acids. To investigate the physiological and clinical significance of this observation, we determined the effect of starvation-induced ketosis on leucine metabolism in obese subjects. Rates of turnover, plasma clearance, and expiratory 14CO2 production (indicator of oxidation) after intravenous infusion of a trace amount of [1-14C]-leucine were measured before and one week after starvation (80 cal/day). This dietary treatment caused a significant increase in the rate of 14CO2 production, but significantly reduced the turnover (9.1 versus 7.0 mmole/hr) and plasma clearance (65 versus 34 L/hr) of leucine. When ketosis was prevented by a daily intake of 300 calories of carbohydrate, the rate of 14CO2 production was significantly decreased. On the other hand, starvation-induced decreases in turnover and plasma clearance of leucine, increases in plasma concentrations of branched-chain amino acids (marker for heightened proteolysis), decreases in plasma concentrations of alanine (marker for stimulated hepatic gluconeogenesis), and decreases in plasma concentrations of glucose and insulin were not prevented until carbohydrate intake was increased to 500 or 800 calories per day. Increases in daily carbohydrate intake (up to 500 calories) were accompanied by decreases in urinary excretion of nitrogen, but not 3-methylhistidine (marker for muscle proteolysis). Our data suggest that: (1) ketosis directly or indirectly enhances oxidation of leucine, (2) starvation-induced ketosis, proteolysis, and gluconeogenesis can be prevented sequentially by carbohydrate diets providing fro 300–800 calories per day, (3) the reduced turnover of leucine in starvation is most likely the result of reduced protein synthesis, and (4) diminution of branched-chain amino acid catabolism is a component of the nitrogen-sparing effect of carbohydrate.

Fatal bacterial endocarditis as a complication of permanent indwelling catheters: Report of two cases

Two cases of endocarditis secondary to permanent indwelling catheters are described. In both cases, the catheters were used for parenteral nutrition and became infected with Staphylococci. Secondary endocarditis developed on the tricuspid and aortic valves. Despite removal of the catheters and appropriate antibiotics, both patients died.

Pyruvate inhibits clofibrate-induced hepatic peroxisomal proliferation and free radical production in rats

In an effort to identify the effects of the 3-carbon compound pyruvate on free radical production, we measured hepatic total peroxisomal beta-oxidation and catalase activity and the production of lipofuscin-like products in male Sprague-Dawley rats consuming an adequate diet supplemented with pyruvate, vitamin E, or the peroxisome proliferator and free radical enhancer clofibrate for 22 days (n = 5 in each group). Clofibrate feeding induced hepatomegaly, a fivefold increase in total peroxisomal beta-oxidation activity, and a threefold increase in hepatic lipofuscin-like products (P < .05). Pyruvate but not vitamin E inhibited the increase in liver size by 70% (P < .05). Both pyruvate and vitamin E completely inhibited clofibrate-induced increases in lipofuscin-like products (P < .05). Pyruvate but not clofibrate or vitamin E increased plasma concentrations of the nitric oxide metabolites nitrite and nitrate (P < .05). We conclude that with clofibrate-induced peroxisomal proliferation and free radical production, pyruvate will inhibit peroxisomal proliferation and free radical production, inhibit free radical-induced lipid peroxidation, and enhance metabolism of nitric oxide.

Preservation injury and acute rejection of rat intestinal grafts: protection afforded by pyruvate

Pyruvate has been shown to prevent intestinal mucosal injury after ischemia-reperfusion. The aim of the present study was to determine whether pyruvate can (1) prevent postreperfusion mucosal injury occurring after intestinal preservation and subsequent transplantation and (2) exert a protective effect on the intestinal graft mucosa during acute rejection. Preservation mucosal injury was evaluated, after 2 hours of reperfusion, by comparing grafts transplanted in a rat syngeneic combination (ACI to ACI) after 2 hours of cold preservation using pyruvate (n = 6) or placebo (n = 6). Mucosal parameters obtained during acute rejection (allogeneic combination: ACI to Lewis) were compared between placebo-treated (n =6) and pyruvate-treated (n = 6) animals. Tissue injury was evaluated by histopathologic examination, oxygen free radical production by luminol-enhanced chemiluminescence, and degree of neutrophil infiltration by myeloperoxidase staining. After reperfusion of the preserved grafts and during acute rejection, mucosal oxygen free radical levels and the number of infiltrating neutrophils were significantly (P <0.05) increased in the untreated grafts, whereas there was a statistically significant inhibition of these parameters in those treated with pyruvate. Mucosal injury, seen after reperfusion of the preserved grafts, was prevented by pyruvate. The histopathologic abnormalities observed in the untreated grafts during rejection were also significantly reduced by pyruvate. Treatment with pyruvate before cold preservation of intestinal grafts, in this rat model, reduced reperfusion mucosal injury, neutrophil infiltration, and oxygen free radical production. Oxygen free radicals were produced in the mucosa of the graft during acute rejection and their production was reduced by pyruvate, which exerted a protective effect on the rejecting allograft mucosa.

Amino acid arterial concentration and muscle exchange during submaximal arm and leg exercise: The effect of dihydroxyacetone and pyruvate

The mixture of dihydroxyacetone and pyruvate (DHAP) is an ergogenic aid that enhances muscle glucose extraction during prolonged aerobic exercise. In order to evaluate the effect of DHAP on muscle amino acid extraction during exercise, we measured arterial concentration and muscle exchange of amino acids in 18 untrained healthy male subjects (aged 20-30 years) performing dynamic arm (60% VO2 max, n = 9) or leg (70% VO2 max, n = 9) exercise to exhaustion with and without dietary supplementation of DHAP. The subjects consumed diets (146 kJ kg body weight-1 day-1) containing either 100 g polyglucose, Polycose (placebo, P) or DHAP (3:1, treatment) substituted for a portion of carbohydrate. The two diets were administered in a double-blind, random, crossover order for a 7-day period. At least 7 days separated the dietary protocols. Blood samples were drawn through radial artery and axillary or femoral vein catheters at rest, during exercise and at exhaustion. Arterial alanine concentration increased by 30% during arm exercise and by 50-60% during leg exercise. No other arterial amino acid concentration changed during exercise. At exhaustion, arterial alanine concentration decreased to pre-exercise levels with arm exercise but remained elevated after leg exercise. Despite changes in arterial concentrations of alanine with exercise, muscle exchange of alanine was not altered with exercise. Exercise did not alter muscle exchange of any amino acid. Arterial amino acid concentrations and muscle exchange of amino acids with exercise were similar with or without DHAP feeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic effects of pyruvate infusion in dogs

PURPOSE Although pyruvate supplementation enhances endurance in humans and increases cardiac output in dogs, its effects on cardiac and peripheral vascular function are not known. Thus, we assessed the cardiovascular effects of pyruvate infusion. MATERIALS AND METHODS Aortic, left ventricular (LV), and pulmonary (Ppa) pressures and LV stroke volume (Svlv; derived from aortic flow probe) were measured after thoracotomy in eight anesthetized dogs. LV area or volume changes were measured using either an epicardial echocardiography (n = 6) or a conductance catheter (n = 2). LV end-systolic elastance (Eeslv) and preload recruitable stroke force (PRSFlv) relations, as estimates of contractility, were generated by transient inferior vena cava occlusion. Simultaneous stroke volume to arterial pressure relations during the occlusions were used to measure arterial elastance (Ea), and steady-state systemic and pulmonary vascular resistances were used as measures of arterial tone. Graded doses of pyruvate (8, 16, and 32 mg/kg/min), dobutamine (positive control) and propranolol (negative control) and placebo (volume control) were sequentially given. RESULTS Dobutamine increased Eeslv, PRSFlv, whereas propranolol had the opposite effect on Eeslv and PRSFlv. Pyruvate at 32 mg/kg/min increased heart rate, Ppa, and SVlv and decreased LV end-diastolic area, and systemic vascular resistance without changing arterial pressure, Eeslv, PRSFlv, or Ea. CONCLUSIONS We conclude that pyruvate infusion in normal dogs induces venodilation but does not alter either cardiac contractility or arterial tone.